Calcitonin stimulates maturation of mammalian growth plate cartilage

To determine whether calcitonin (CT) might effect maturation of mammalian growth plate cartilage, we administered salmon CT (sCT) to young rats and used the growth plate from the distal metatarsal as our in vivo growth plate model. Growth plate alkaline phosphatase activity and histological examination were assessed after 3 days of sCT treatment. Alkaline phosphatase activity, a marker of hypertrophied chondrocytes, increased 85%, and the zone of maturation enlarged in rats receiving sCT. In addition, sCT treatment was associated with an increased growth plate 35SO4 incorporation 84% above animals receiving buffer alone. We tested whether this might be a direct effect of CT by using an in vitro model, the growth plate from the fetal pig scapula. Organ culture of these cartilages in serum-free medium with and without sCT (1 U/ml) was performed for 3 days. sCT stimulated alkaline phosphatase activity 49% above growth plates incubated in medium alone. Furthermore, sCT treatment increased the number of hypertrophied chondrocytes leading to widening of the zone of maturation. These studies suggest that CT might have a role growing mammals by promoting maturation of growth plate cartilage.